The Simple Difference Between Ballistic Missiles and Cruise Missiles

A man at a railway station in Seoul, South Korea, watches news showing file footage of North Korea's missile launch on Feb. 12, 2017. Jung Yeon-Je/AFP/Getty Images
A man at a railway station in Seoul, South Korea, watches news showing file footage of North Korea's missile launch on Feb. 12, 2017. Jung Yeon-Je/AFP/Getty Images

Last weekend, North Korea unexpectedly staged a test launch of a new ballistic missile, the Pukguksong-2. The launch took place during a state visit to the United States by Japanese Prime Minister Shinzo Abe, which led to President Donald Trump turning the restaurant at Trump's Mar-a-Lago private resort in Florida into an impromptu situation room.

It was North Korea's latest act of defiance against a 2006 U.N. Security Council resolution barring it from developing ballistic missiles. And although the 310-mile (499-kilometer) launch from North Korea to the Sea of Japan didn't pose any actual threat to North America, according to the U.S. Strategic Command, it did further add to the anxiety about how to keep the isolated, paranoid North Korean regime from developing the ability to launch a nuclear attack.

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This photo taken on Feb. 12, 2017, was released by North Korea's official Korean Central News Agency and shows the launch of a surface-to-surface medium long-range ballistic missile Pukguksong-2 at an undisclosed location.
STR/AFP/Getty Images

And for many Americans, the ballistic missile may have raised another question. What exactly is a ballistic missile, anyway? Is there something about the ballistic part that makes a missile even more dangerous? After all, when someone freaks out we say they've "gone ballistic."

According to the Federation of American Scientists, a ballistic missile is one that has a ballistic trajectory over most of its flight path. What that means is that once the missile burns up the fuel that propels it, the missile keeps moving, the same way that a bullet does after it's been fired out of a gun. Once the fuel is gone, the missile's direction can't be altered. It follows a path determined by the speed of its launch and the force of gravity trying to pull it back toward the Earth's surface. Eventually, gravity guides the missile — and its payload, which might be an explosive, a chemical or biological weapon, or a nuclear device — down toward its target.

Ballistic missiles are different than cruise missiles. Like the one launched by Russia earlier this week, cruise missiles are self-propelled for the majority of their time in the air, flying in a relatively straight line and at lower altitudes thanks to a rocket propellant. Think of a ballistic missile's flight path as a large arc up and back down again, while that of a cruise missile — fired from a warship, for instance — is closer to a straight line.

Ballistic missiles first came into use during World War II, when the Germans used a ballistic missile called the V-2 to attack London. British air defenses designed to stop aircraft couldn't stop the V-2s, because the rockets travelled too high into the upper atmosphere and moved too fast. After the war, the U.S., with the help of captured German technology and scientists, built its own arsenal of even more powerful intercontinental ballistic missiles (ICBMs) capable of unleashing nuclear destruction upon targets on the other side of the world. The Soviet Union and China built ICBMs as well, setting up a world where a nuclear war was deterred by the prospect of mutual assured destruction.